Scientists have long pondered how extremely bright, ancient galaxies known as submillimeter galaxies (SMGs) managed to pump out stars 1,000 times faster than the Milky Way does today.

Two theories have dominated the debate. The first is that galaxy collisions drove short-lived, but spectacular bursts of star formation. The other idea is that SMGs are long-lived structures that accumulated mass over time.

"Neither scenario has been successful in fully replicating the observed properties of SMGs," astronomer Romeel Dave, with the University of the Western Cape, Cape Town, South Africa, wrote in an essay in this week's Nature.

A new study, also published Nature, details a computer simulation that, for the first time, matches observed properties of SMGs. The model shows that the galaxies aren't transient and that they can generate stars at the incredible rate of 500- to 1,000 solar-mass stars PER YEAR for a billion years.

What makes them so productive? The simulation suggests the galaxies, which date back to about 3 billion years after the Big Bang, tapped reservoirs of gas to form new stars, rather than rely on mergers with other galaxies.

"In a nutshell, the authors find that SMGs plausibly arise from a ‘perfect storm' of high rates of gravitationally driven gas accretion, the recycling of previously ejected material and contributions to the systems' submillimetre luminosity from nearby galaxies," Dave wrote.

Image depicting the distribution of galaxies across the infrared luminous region, at a given instance in time, with colors denoting gas density. A new study suggests that extreme infrared-luminous regions observed by submillimetre-wave telescopes are often comprised of groups of galaxies in the early universe that will grow to be massive clusters of galaxies at the present day.

March 13, 2013, marks 20 years since the W. M. Keck Observatory began taking observations of the cosmos. Located in arguably one of the most extreme and beautiful places on the planet -- atop Mauna Kea, Hawai'i, 13,803 ft (4,207 m) above sea level -- the twin Keck domes have observed everything from asteroids, planets, exoplanets to dying stars, distant galaxies and nebulae. Seen in this photograph, the Keck I and Keck II telescopes dazzle the skies with their adaptive optics lasers -- a system that helps cancel out the turbulence of the Earth's atmosphere, bringing science some of the clearest views attainable by a ground-based observatory.

To celebrate the last two decades of incredible science, Discovery News has assembled some of the most impressive imagery to come from Keck.

A nice image of Saturn with Keck I telescope with the near infrared camera (NIRC) on Nov. 6, 1998. This is a composite of images taken in Z and J bands (1.05 and 1.3 microns), with the color scaling adjusted so it looks like Saturn is supposed to look to the naked eye.

This is Saturn's giant moon Titan -- a composite of three infrared bands captured by the Near Infrared Camera-2 on the 10-meter Keck II telescope. It was taken by astronomer Antonin Bouchez on June 7, 2011.

This image of Neptune and its largest Tritan was captured by Caltech astronomer Mike Brown in September 2011. It shows the wind-whipped clouds, thought to exceed 1,200 miles per hour along the equator.

A color composite image of Jupiter in the near infrared and its moon Io. The callout at right shows a closeup of the two red spots through a filter which looks deep in the cloud layer to see thermal radiation.

HR 8799: Three exoplanets orbiting a young star 140 light years away are captured using Keck Observatory's near-infrared adaptive optics. This was the first direct observation by a ground-based observatory of worlds orbiting another star (2008).

This is WR 104, a dying star. Known as a Wolf Rayet star, this massive stellar object will end its life in the most dramatic way -- possibly as a gamma-ray burst. The spiral is caused by gases blasting from the star as it orbits with another massive star.

Galaxy cluster Abell 2218 is acting as a powerful lens, magnifying all galaxies lying behind the cluster's core. The lensed galaxies are all stretched along the shear direction, and some of them are multiply imaged.

The central starburst region of the dwarf galaxy IC 10. In this composite color image, near infrared images obtained with the Keck II telescope have been combined with visible-light images taken with NASA’s Hubble Space Telescope.